1. Field of the Invention
This invention relates to an illumination device of gradual dimming after power interruption, particularly to an illumination device having a built-in power storage unit in which power is supplied by the built-in power storage unit when city power is interrupted, and light intensity of the light source of the illumination device is gradually dimmed by the control conducted from a gradual-dimming light intensity drive control unit.
2. Brief Description of Prior Art
Illumination lamp has been used to provide enough light intensity in dark, dim or light-inadequate place so that people can conduct activity smoothly. However, casual maintenance on power supply equipment conducted by power supplier or natural or artificial damage happened on power supply equipment often result in power interruption. In this case, people accidentally entrapped in the environment of completely dark, dim or insufficient illumination are apt to feel uneasy, even are vulnerable.
Therefore, an emergency light has been designed as a measure which is supplied with power from its interconnected charging device. However, this emergency light is not integrated with the indoor illumination lamp so that consumer has to buy it at additional expense. Since the emergency light has to be installed inside the house, inconvenience maybe happened, what is more, the total indoor space planning is also negatively influenced.
Moreover, an illumination unit including power supplying element inside is disclosed in US Patent Application No. 2009039788(A1) in which power is supplied to the light emitting unit in case of power interruption. The illumination unit has a light emitting device comprising (a) a power source input end for receiving external power came from outside power source; (b) a solid state light emitting element connected to the power source input end; and (c) a backup power source connected to the solid state light emitting element, which can supply power to the solid state light emitting element when the solid state light emitting element is unable to receive power from the power source input end. However, the solid state light emitting element in this structure provides light for illumination in stable luminance manner such that it consumes more power. Thus, the power stored in the backup power source will soon be consumed up in short period so that user is unable to cope with the power interruption with sufficient time.
Otherwise, there is a product sold in the market that is added with a delay circuit for delay the timing of lamp's turn-off under the state of switching the power switch to ‘OFF’ such that user has a buffer period before light extinguishing. However, when the illumination lamp with this structure delays the illumination, the illumination lamp is also used to illuminate space with the same luminance as that generated by city power normally. There is still a possibility of light turn-off by accidental power interruption such that people accidentally entrapped in the environment of completely dark, dim or insufficient illumination are apt to feel uneasy, even are vulnerable.